This invention relates to a method of obtaining an X-ray computerized-tomographic image and an apparatus for utilizing the above method, in which desirable regions of interest within tomographic images of an object are automatically enlarged and displayed at a correct position on the monitor screen.
The conventional X-ray computerized-tomographic apparatus set forth in the preamble has a function of displaying a scannogram and a tomographic image. That is, before data acquisition of the tomographic images of a diseased portion of the object under examination, the scannogram, which covers a wide region including that portion, is produced based upon the X-ray transmission detection signal. By observing the scannogram, positions for imaginary slices of the object, i.e., slice positions, for which the tomographic images are to be obtained are determined, and the tomographic images are obtained by reconstructing the other detection signal based upon the determined slice positions.
Further, when reconstructed tomographic images of the slice positions are observed, there may arise a necessity of enlarging part of an images (which are referred to as "interest regions") for the purpose of diagnosis. In this case, enlarged image are obtained from the other projection data (detection signal), which has been acquired in advance, by determining a center of the interest region for each tomographic image.
As previously described, in the conventional computerized-tomographic apparatus, when it is desirable to observe an enlarged tomographic image for the purpose of diagnosis, a center of the enlarged image of the interest regions must be determined for each of the tomographic images, which is a cumbersome task. Further, the operation of obtaining the enlarged images of the interest regions is also cumbersome. More particularly, first a scannogram is obtained, then slice positions are determined by observing the scannogram, and thereafter tomographic images are reconstructed. Subsequently the centers of the tomographic images of the interest regions which are to be enlarged are determined to obtain the enlarged image by observing the reconstructed tomographic images. Therefore, a long operation time is required until the enlarged image of the interest region is obtained from the projection data. Moreover, the patient must endure this long examination time.
An object of the invention is to provide an X-ray CT diagnostic apparatus which may overcome the conventional drawbacks described above and may permit a display of the enlarged tomographic images of the interest regions within the slice positions of the object in such that the centers of the enlarged interest region are always at the center of the display screen.